linux-kernel - Re: [PATCHv3 5/7] parisc64: Add .opd based function descriptor dereference

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Message-ID: <20171019064425.GC449@jagdpanzerIV>
Date:   Thu, 19 Oct 2017 15:44:25 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        James Bottomley <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jessica Yu <jeyu@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        linux-ia64@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 5/7] parisc64: Add .opd based function descriptor
 dereference

On (10/04/17 12:40), Petr Mladek wrote:
> > +unsigned long dereference_module_function_descriptor(struct module *mod,
> > +						     unsigned long addr)
> > +{
> > +	unsigned long start_opd = (Elf64_Addr)mod->core_layout.base +
> > +				   mod->arch.fdesc_offset;
> > +	unsigned long end_opd = start_opd +
> > +				mod->arch.fdesc_count * sizeof(Elf64_Fdesc);
> 
> I know that this is used in rather slow paths. But it still might
> make sense to have these section borders pre-computed and
> stored in struct mod_arch_specific. I mean to do similar
> thing that we do on powerpc.
> 
> Well, we could do this in a followup patch if parisc people
> wanted it.
> 
> 
> > +	if (addr < start_opd || addr >= end_opd)
> > +		return addr;
> > +
> > +	return dereference_function_descriptor(addr);
> > +}
> > +#endif
> 
> Otherwise the patch looks fine to me.
> 
> Reviewed-by: Petr Mladek <pmladek@...e.com>

let's do it later, if need be.

	-ss